GIACIATION OF PRINCE WILLIAM SOUND 475
The bar at the northern end of Latouche Passage has depths of 168 to 330 feet in mid-fiord, in contrast with 636 to 642 feet a half mile distant on each side. It is narrow and straight, completely closing the mouth of the fiord excepting for a 480 foot channel north of the middle. It may be explained equally well as either (a) a moraine bar or (b) an uneroded rock ledge with a rock basin southwest of it, though its position is not as favorable to the latter interpretation as in the case of the bar at the seaward end of the same fiord. If it is a submerged moraine it might have been built at the terminus of a southwest-retreating local glacier, fed by the cirques of Latouche Island, or as a lateral moraine of the northwest-retreating ice tongue of Knight Island Passage.
The Ice-Sculptured Outlets of Prince William Sound. The ice of the piedmont glacier of Prince William Sound had three outlets to the Pacific Ocean, (1) Montague Strait and the four adjacent fiords alluded to in the last section, (£) Hinchinbrook Entrance, and (3) the mouth of Orca Inlet.
The outlet by Montague Strait, was probably the largest one. It was not as important, however, as it would have been had there not been four subordinate outlets. This is shown by the fact that this outlet was only eroded to a maximum depth of 1100 feet and shallows to 400 feet near the Pacific Ocean. Its width is from 5 to 6 miles and the deepest channel is close to Latouche Island, perhaps because of the influence of local glaciers on Montague Island. The southeastern slope of Latouche Island is, therefore, smoothed and much oversteepened, sloping at the rate of 3500 to 4000 feet to the mile on the land. The slope continues below water at the rate of 1600 feet to the mile, beyond which Montague Strait has a broad, flat bottom with an equally steep ascent to Montague Island. This U-shape indicates that it was the work of a glacier which sculptured Montague Strait, as do the submerged hanging valleys, for example, Harming Bay and Macleod Harbor, on the southwestern side of Montague Island, which are each 132 feet deep at their mouths and hang 528 and 330 feet, respectively, above Montague Strait.
The central outlet was between Hinchinbrook and Montague Islands. Hinchinbrook Island, which has also been called Nutcheck Island, is separated from Montague Island by a strait 7 to 10 miles wide, called Hinchinbrook Entrance. It has also been called Meiklejohn Entrance. The strait has a length of about twelve miles and is 900 to 1300 feet deep.1 Its cross-section is a typical glacial U, for in the narrowest part there is an abrupt descent of 900 feet within £ to f of a mile of each shore and a fiat, aomewhat-basined bottom five miles wide. The lower slopes of the land are similar to the slopes below tidewater, for example, the precipitous character of Bear Cape on the eastern side of Hinchinbrook Entrance north of Port Etches, which is interpreted as a result of glacial oversteepening,
There are submerged hanging valleys on each side of Hinchinbrook Entrance. On the west are Eocky and Zaikof Bays, with maximum depths of 342 and 324 feet, submerged hanging valleys whose discordant junction with Hinchinbrook Passage, amounts to from 600 to 700 feet.
Port Etches east of Hmchinbrook Entrance also shows a discordant relationship, having a submerged hanging valley lip, with a descent of 818 feet to the bottom of Hinchinbrook Entrance, the water increasing in depth from 806 to 624 feet in less than one and one-half miles.
i See U. S. Coast and Geod. Survey Charts, Nos. 8500, 8515, and 8520.